1. Field of the Invention
The present invention relates to the earthboring arts. More particularly, the invention relates to apparatus and methods for petroleum well completion and preparation of a well for petroleum fluid production.
2. Description of Related Art
Pursuant to one procedure of petroleum well completion, after the well borehole is complete, an outer well casing is set within a cement annulus between the raw borehole wall and the outer surface of the casing pipe. Thereafter, the casing pipe and cement annulus are perforated into the formation production zone to provide petroleum fluid flow channels from the formation past the cement and pipe wall into the interior bore of the casing.
Although the cemented casing substantially stabilizes the formation production face, substantial quantities of formation debris may nevertheless be produced through the perforations. To suppress the transfer of formation debris into production flow tubing, it has become a practice to set a liner casing within the outer casing. Along the zone of petroleum production, the liner casing includes perforated pipe sections called screens. The screens may, in fact, be sections of pipe that are slotted with numerous, narrow slits or drilled with numerous small holes. Additionally, an annular space around the screens between the inner bore of the outer casing and the outer surface of the liner casing is packed with relatively large particulates to provide a gravel bed filter ahead of the screens.
In a related completion practice, the petroleum production flow rate from relatively narrow production zones is enhanced by drilling the wellbore along the zone strata to increase the production face area. In some cases, this practice may require the wellbore to follow a substantially horizontal directional course. Placing a gravel pack around the casing liner screens of a horizontal production face becomes a serious challenge due to an inadequacy of circulation fluid flow area. As the gravel is flowed into the inner annulus for well deposit between the screens and the casing perforations, a threshold flow velocity must be maintained to transport the gravel aggregate in a fluidized suspension to all regions of the gravel pack annulus. However, the fluid suspension medium that carries the gravel into the gravel pack annulus must pass through the screens in return circulation. At the threshold flow rates essential to a horizontal gravel pack completion, the screen flow area is insufficient for supporting the fluidized gravel transport.
Increasing the circulation flow area of a subliner screen by quantities that by most, would be considered adequate, would also compromise the gravel retention quality of the screen. It is, therefore, an object of the present invention to provide such an increase flow area for the gravel packing interval. Correspondingly, it is an object of the invention to provide a means for closing the auxiliary flow area after the gravel packing process is completed.
The present invention addresses these objectives and others that will become apparent from the detailed description to follow. In brief, however, large flow area apertures are provided in screen base pipe, preferably near the pipe joint ends. Underlying these large flow apertures within the base pipe bore is a malleable material sleeve. The sleeve is positioned with an outside diameter that is smaller than the inside diameter of the base pipe bore by a differential sufficient to provide a fluid flow annulus of adequate circulation flow area. One axial end of the sleeve is flared or flanged to provide a radial rim that projects radially past the inside diameter of the base pipe. When adjacent base liner pipe joints are assembled by a threaded pipe coupling, the outer rim elements of the sleeve flange are clamped between the contiguous pipe ends to structurally support and confine the sleeve. Alternatively, the rim of the sleeve flare may be welded to the internal bore of the base pipe.
Near the xe2x80x9cfreexe2x80x9d end of the sleeve opposite from the flange, an O-ring sealing element is provided around the sleeve outer perimeter.
The screen pipe is set with the sleeve annulus open to the large flow area apertures. After the gravel pack is placed around the screen, the large flow area apertures are closed by swaging the sleeve radially out against the inner bore wall of the base pipe. Such external radial swaging presses the sleeve O-ring seal against the pipe borewall to seal the annulus and thereby seal the large flow area apertures from the base pipe liner bore.
The sleeve swaging procedure may be carried out by one of several types of swaging tools. One example of a suitable swaging tool includes a fluid expansible element that is attached to a completion tool string or coiled tubing. The expansible element is similar to an expandable, well annulus packer that expands to seal the annulus of a wellbore around an internal tube. Highly pressurized fluid pressure developed at the wellhead and delivered down the completion string tube bore expands the swaging tool within the sleeve.
Another example of a swaging tool type that is suitable for the present invention is a conical or spherical shaped material forming tool that is releasably secured within a casing end-shoe. The cross-sectional diameter of the forming tool is sized in appropriate correspondence with the desired internal diameter of the expanded sleeve. An appropriate connection tool is attached to the end of the well completion tube. When timely, the completion tube is lowered through the sleeve opening for a bayonet connection with the swaging tool. Withdrawal of the completion tube draws the larger diameter swaging tool through the smaller sleeve opening thereby stretching the sleeve inside diameter.
A third suitable swaging tool type comprises a tapered mandrel within a collet element. The swage is attached to the completion string and is in a collapsed alignment while descending downhole. Upon reversal of the completion string travel direction, the internal mandrel is shifted axially relative to the collet thereby expanding the collet fingers.